1. Technical Field
The present invention relates to a computer display switching circuit and a method thereof and, more particularly, to a computer display switching circuit which detects the connection of an external cathode ray tube (CRT) and the opening and closing of a liquid crystal display (LCD) cover and automatically switches a display, and a method thereof.
2. Related Art
In general, a notebook computer includes a body composed of a computer system and a key board, and a cover connected to the body. An LCD display device is installed inside the cover, and a connector to an external CRT monitor is installed in the body.
As explained below, the operation of the notebook computer is such that it is difficult or inconvenient to maintain the external CRT monitor in the "power-on" state when the cover of the LCD display device is closed. That is to say, when the cover to the LCD display device is closed, the CRT monitor is automatically powered down, and it is only by operation of a hot key on the keyboard that the user is able to maintain or restore the external CRT monitor to its "power-on" state.
In addition, the notebook computer operates in such a manner that, when the computer is not in use, system power remains on. As a result, power is unnecessarily consumed by the notebook computer.
Therefore, there is a need for development of a display switching circuit for a computer system and a related method in which selection of a display is automatically switched without operating a keyboard, and in which unnecessary power consumption by the notebook computer is avoided.
The following patents are considered to be representative of the prior art, but are burdened by the disadvantages discussed above:
U.S. Pat. No. 5,483,250 to Herrick entitled Projection Display System for a Laptop Computer or a Notebook Computer; U.S. Pat. No. 5,481,732 to Shahbazi entitled CRT Monitor Power Control Unit; U.S. Pat. No. 5,548,765 to Tsunoda, et al. entitled Power Saving Display Subsystem for Portable Computers; U.S. Pat. No. 5,459,833 to Nishizawa entitled Display Control System; U.S. Pat. No. 5,337,212 to Barlett, et al. entitled Flip Screen for Notebook Computer; U.S. Pat. No. 5,319,582 to Ma entitled Detachable Portable Personal Computer; U.S. Pat. No. 5,335,168 to Walker entitled Computer System with Power-down Mode for Monitor, U.S. Pat. No. 5,184,314 to Kelly, et al. entitled Mobile Data Processing and Communications System with Removable Portable Computer, U.S. Pat. No. 5,267,123 to Boothroyd, et al. entitled Case for Portable Computer Having Display Accessible When Lid Is Closed over the Keyboard; U.S. Pat. No. 5,235,532 to Sugino entitled Information Processing Apparatus for Performing Operations in Response to the Opening and the Closing of a Cover Thereof; U.S. Pat. No. 5,200,913 to Hawkins, et al. entitled Combination Laptop and Pad Computer; U.S. Pat. No. 4,852,498 to Judd entitled Lap Top Computer Work Station; U.S. Pat. No. 4,839,837 to Chang entitled Three Layered Laptop Computer; U.S. Pat. No. 4,860,246 to Inoue entitled Emulation Device for Driving a LCD with a CRT Display; and U.S. Pat. No. 4,903,222 to Carter, et al. entitled Arrangement of Components in a Laptop Computer System.